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Genetics Exam 2 Part 4
Terms in this set (45)
what is the central dogma of molecular genetics? name the best known exception to the dogma.
DNA to RNA to Protein
retroviruses or the exception: RNA to DNA to RNA
what does mRNA stand for and when was it discovered?
discovered in 1961
how can 4 nucleotide letters specify 20 amino acids
three letter genetic code
Define codon and anti codon. which molecules carry these?
codon: three nucleotides that encode the genetic sequence in DNA or RNA- found in mRNA
anticodon: three nucleotides that encode the genetic sequence for TRANSFER RNA (corresponds to a complimentary codon in mRNA)
the genetic code is composed of ___ letters, the nucleotides. They are ___,____,____ and ___. These letters are organized in "words", called _______, which encodes for _____ different amino acids. ______ codons encode for amino acids and ____ are stop codons
explain "the genetic code is linear"
the sequence of nucleotides is linear
explain "the genetic code is unambiguous"
each triplet only codes for one amino acid
explain "the genetic code is degenerate"
a given amino acid can be coded by multiple codons
explain "the genetic code has punctuation but is commaless"
once translation begins, codons are read one after the other with no breaks in between. the stop codons represent the period at the end of the sentence
explain "the genetic code is not overlapping"
any nucleotide is only apart of one triplet
the genetic code is co linear with _____
the amino acid sequence
explain the wobble principle
the first two letters of a codon are more critical than the third letter
explain the ordered nature of the genetic code
chemically similar amino acids differ by the middle base. This is to act as a buffer to the effects of mutation
explain how the genetic code is nearly universal
applies to nearly all living animals
what are initiation and stop codons? explain their meaning for the process of translation
initiation= start codon- an mRNA sequence (usually AUG) that signals the beginning of translation
stop codons: a triplet within the sequence codes for the end of termination
how many initiation codons do prokaryotes have? And how many are there in eukaryotes?
prokaryotes: 2 (AUG)(GUG)
Eukaryotes: 1 (AUG)
What is a nonesense mutation?
inserting a termination codon into the DNA sequence
what is the relationship between the codon sequence in the DNA molecule and the amino acid sequence in the polypeptide/protein?
polypeptides are chains made of amino acids and these chains make up proteins?
true or false? the mammalian genome is composed of 20,000 protein coding genes. Thus it encodes for 20,000 proteins
False, it would encode for millions of proteins
explain the term "reading frame" and how it determines the number of proteins encoded
the reading frame divides the sequence of nucleotides into non overlapping triplets - establishes the code for proteins
true or false? transcription is the process of RNA synthesis from a DNA template in the nucleus
true or false? mRNA, or mature RNA, can only be found in the cytoplasm of the cell
false, mRNA is messenger RNA
True or False? ribosomes are responsible for mRNA synthesis in the cytoplasm
false, rRNA are responsible
True or false? the amount of protein is proportional to the amount of mRNA in a cell
true or false? DNA polymerase is responsible for the transcription process
False, RNA polymerase
True or False? contrary to DNA replication, RNA synthesis does not require primers
true, use of codons
RNA polymerase cannot directly bind to DNA. Which molecules help RNA polymerase interaction with DNA to initiate transcription?
What is the name of the DNA sequence where RNA polymerase and transcription factors bind to initiate transcription
Explain how the newly synthesized RNA molecule is elongated what is the direction of the process?
5' to 3'
what is the enzyme responsible for driving the elongation process of RNA
How many RNA polymerases are there in eukaryotes? what are their products?
RNA polymerase 1: rRNA and tRNA
RNA polymerase 2: mRNA
RNA polymerase 3: tRNA
why does transcription need chromatin remodeling in order to be initiated in eukaryotes
because of how condensed it is, specific genes cant be reached by RNA polymerase, so it must open
what does cis-action mean? name cis-acting factors in eukaryotic transcription
non-coding DNA that regulate transcription of neighboring genes
promoters and enhancers
what does trans-action mean? name trans-acting factors in eukaryotic transcription
regulate expression of distant genes
describe the caps and tails added to the RNA after transcription. How are they important for the newly synthesized RNA molecule?
5' cap: assist in RNA transport
3' poly a tail: protects the mRNA from degradation
true or false? Even though prokaryotes dont have introns, splicing occurs with the removal of segments of RNA that are not translated into proteins
false- prokaryotes dont have introns.
by definition, splicing it the removal of introns
do mitochondrial genes have introns? is mtDNA more similar to prokarotic or eukaryotic genes with regards to introns?
no, mtDNA has no introns, more similar to prokaryotic i guess
do all eukaryotic genes have introns? give examples
most eukaryotic genes contain introns with the exceptions of:
histone genes, interferon genes, male sex determination gene (SRY)
explain the process of alternative splicing. Why is it important?
splice out the introns in different locations, which makes the final code different
even tho it's the same mRNA
name the three traditional classes of RNA and describe briefly the function of each
rRNA: synthesizes ribosomes
mRNA: carries genetic info from DNA to ribosome
tRNA:carries amino acids to ribosome
name the main classes of non-coding RNAs
small non-coding RNAs
they regulate gene expression
what does ENCODE stand for
the encyclopedia of DNA elements
what was the main goal of the human encode process?
identify all functioning elements in the human genome
based on the findings of ENCODE, what is the main product of gene activity and how does this compares with the central dogma
the majority of DNA codes for RNA
name transcriptional and post transcriptional mechanisms that allow limited number of genes to encode for millions of proteins.
Transcriptional: overlapping genes, sharing exons between genes
Post-transcriptional: alternative splicing
THIS SET IS OFTEN IN FOLDERS WITH...
Genetics Exam 2 Part 2
Genetics Exam 2 Part 1
Genetics Exam 2 Part 3
Genetics Exam 2 Part 5/6
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